Process for preparing oil-extending rubber

ABSTRACT

An oil-extended polyisoprene composition which comprises A. 100 PARTS BY WEIGHT OF A SYNTHETIC CIS-1,4-POLYISOPRENE WHICH HAS BEEN PREPARED BY POLYMERIZING ISOPRENE IN SOLUTION IN A HYDROCARBON WITH AN ORGANOMETALLIC MIXED CATALYST OF TITANIUM TETRACHLORIDE, AN ALUMINUM TRIALKYL AND/OR AN ALUMINUM TRIALKYL ETHERATE AND STOPPING THE POLYMER SOLUTION CONTAINING THE MIXED CATALYST WITH AN ALIPHATIC OR CYCLOALIPHATIC DIAMINE OR POLYAMINE AND AN ALIPHATIC OR CYCLOALIPHATIC SECONDARY AMINE CONTAINING AT LEAST 10 CARBON ATOMS, OPTIONALLY IN ADMIXTURE WITH A LOWER ALIPHATIC ALCOHOL, FOLLOWED BY STABILIZATION WITH A CONVENTIONAL ANTI-AGER, AND B. FROM 15 TO 50 PARTS BY WEIGHT OF A RUBBER EXTENDING OIL AND A PROCESS FOR PRODUCING SAID MIXTURE.

United States Patent Witte et al.

[54] PROCESS FOR PREPARING OIL- EXTENDING RUBBER Inventors: Josef Witte, Cologne, Stammheim; Friedrich Haas, Cologne, Buchheim; Gunter Marwede, Leverkusen, all of Germany Assignee: Farbenfabriken Bayer Aktiengesellschaft, Leverkusen, Germany Filed: July 22, 1969 Appl. No.: 843,807

Foreign Application Priority Data Aug. 6, 1968 Germany ..P 17 95 068.4

References Cited UNTTED STATES PATENTS 1/1965 Kahn et al. ..260/94.3

[ Aug. 29, 1972 Primary ExaminerMorris Liebman Assistant Examiner-H. H. Fletcher Attorney-Connolly and Hutz [57 ABSTRACT An oil-extended polyisoprene composition which comprises a. 100 parts by weight of a synthetic cis-1,4- polyisoprene which has been prepared by polymerizing isoprene in solution in a hydrocarbon with an organometallic mixed catalyst of titanium tetrachloride, an aluminum trialkyl and/or an aluminum trialkyl etherate and stopping the polymer solution containing the mixed catalyst with an aliphatic or cycloaliphatic diamine or polyamine and an aliphatic or cycloaliphatic secondary amine containing at least 10 carbon atoms, optionally in admixture with a lower aliphatic alcohol, followed by stabilization with a conventional anti-ager, and

b. from 15 to 50 parts by weight of a rubber extending oil and a process for producing said mixture.

8 Claims, No Drawings PROCESS FOR PREPARING OIL-EXTENDING RUBBER Oil-extended rubbers based on natural rubber or cisl,4-polyisoprene are of commercial and economic interest. Unfortunately, considerable difficulties are involved in the large-scale production of natural rubberoil blends, as the vulcanisate properties of such blends are unsatisfactory. Tensile strength, modulus, elasticity and structural strength are all far from adequate. As with natural rubber-oil blends, the commercially available oil-extended synthetic cis-l,4-polyisoprenes of the lithium and titanium type yield vulcanisates with unsatisfactory properties.

This invention relates to mixtures of a. 100 parts by weight of a synthetic cis-l,4- polyisoprene which has been prepared by polymerising isoprene in solution in a hydrocarbon with an organometallic mixed catalyst of l. titanium tetrachloride and 2. an aluminum trialkyl and/or an aluminum trialkyl etherate, and stopping the polymer solution containing the mixed catalyst with an aliphatic or cycloaliphatic diamine or polyamine and an aliphatic or cycloaliphatic secondary amine containing at least 10 carbon atoms, optionally in admixture with a lower aliphatic alcohol, followed by stabilization with a conventional anti-ager, and b. from l5 to 50 parts by weight of an aliphatic, naphthenic or aromatic rubber extending oil.

One object of the invention is a process for producing a cis-l,4-polyisoprene-rubber extending oil blend which comprises a. Polymerising isoprene in solution in an inert aliphatic, cycloaliphatic or aromatic hydrocarbon solvent using an organometallic mixed catalyst based on titanium tetrachloride, an aluminum trialkyl and/or an aluminum trialkyl etherate.

b. inactivating said catalyst at the end of the polymerization by adding 0.05 to 0.5 percent by weight based on polyisoprene of an aliphatic or cycloaliphatic dior polyamine and simultaneously or subsequently 0.1 to 1 percent by weight based on polyisoprene of a secondary aliphatic or cycloaliphatic monoamine containing at least carbon atoms c. incorporating from to 50 parts by weight based on polyisoprene of a rubber extending oil.

d. recovering the polyisoprene-rubber extending oil blend from the obtained solution by removing the solvent.

In one embodiment a lower aliphatic alcohol may be added additionally in step (b).

The polymerization step (a) may be carried out in a conventional way by first providing the solvent (which is a hydrocarbon such as n-hexane, mixtures of alkane hydrocarbons, benzene, toluene or similar solvents) and introducing the catalyst components. Preferably the titanium tetrachloride and the trialkyl aluminum (alkyl meaning preferably alkyl having one to six carbon atoms) and/or aluminum trialkyl etherate (e.g., with dibutyl ether) are added simultaneously. The molar ratio of titanium to aluminum is preferably 1 1.5 to l 0.7. The amount of ether, if any, should be sufficient to form the etherate. The catalyst solution thus produced is introduced into a solution of 8 to ZOpercent of isoprene in the same solvent and polymerization is effected at temperatures of between 0 and 30C. There is obtained a solution of cis-l,4- polyisoprene.

The inactivation step (b) may be carried out by adding the amines dissolved in an inert solvent, preferably the solvent used in the polymerization step. The concentration of the amine solution may be between 1 and 20 percent by weight. There are several modes of operation, e.g., a solution of the dior polyamine may be added first, followed by an optional washing of the resulting solution with water (in order to remove water soluble catalyst residues) and the solution of the monoamine and the antiager may be added subsequently. Also one solution containing both amines may be added.

Diamines or polyamines (this term meaning preferably triand tetraamines) which may be used in this invention are e.g., aliphatic dior polyamine containing saturated aliphatic hydrocarbon radicals with one to 10 carbon atoms or cycloaliphatic radicals having five to seven carbon atoms. Examples of these amines are l,2-diamino ethane; l,2-di(methylamino)- ethane; bis-( 2-aminoethyl)-amine; l ,l l-diamino- 3,6,9triazodecane; 1,3-diamino propane; bis-(2- aminopropyl)-amine; 1,4-diamino butane; 1,6-diamino hexane; and 1,4-diamino cyclohexane.

Secondary monoamines are aliphatic or cycloaliphatic secondary amines containing a total of at least nine carbon atoms, preferably 9-25 carbon atoms. Examples of such amines are: di-2-ethylhexyl amine, dicyclohexyl amine and, preferably, N-methyl stearylamine, or other derivatives of methylamine with a linear or branched alkyl radical containing more than nine carbon atoms or mixtures thereof.

In some cases it may be of advantage to add a lower aliphatic alcohol such as methanol, ethanol or isopropanol to the amines in order to improve their solubility. The amount of this alcohol may e. g. be between 10 to percent by weight based on the amines.

In step (c) the rubber extending oil is added. This adding is effected at temperatures of between 10 and 50C. Care must be taken to effect a thorough mixing with the rubber solution.

Suitable rubber extending oils are the paraffinic, naphthenic or aromatic mineral oils, customarily used in the rubber industry or their intermediates, oils of vegetable origin' such as linseed oil, synthetic hydrocarbons and other synthetic plasticizers. They may suitably be characterized by their viscosity-density constant (VDC), the following main distinctions being made:

Classification Viscosity density constant of mineral oils Preferred rubber extending oils are 1. Mineral oil plasticisers a. Predominantly paraffinic components Density d (g/ml) 55% by weight 0.85-0.95

Refractive index (n 1.465-l.490 Aniline point (AP C.) 90-127 Refraction intercept (n -0.5 d3) 1.048 Viscosity/density constant (D-O, 24-0, 022 log. (V,35.5))/0.755 0.78-0.84 b. With high naphthenic components 25% by weight of cycloaliphatics Density d (g/ml) 0.87l.0 Refractive index (n,,") 1.50-1.57 Aniline point (AP C.) 30-90 Refraction intercept (n -0.5 d3") 1.042-l.060 Viscosity/density constant (DO.240.022 log.(V 35.5))/O.755 0320-0910 c. With a large component of aromatic hydrocarbons Density d (g/ml) O.960 Refractive index (n 1.55-1.60 Aniline point (AP C.) 5-35 Refraction intercept (n -0.5 d 1.055 Viscosity-density constant (D-0.240.22 log. (V -35.5))/0.755 0.901

2. Synthetic hydrocarbons:

a. Saturated hydrocarbons, for example polyisobutylenes or copolymers of isobutylene, l-butene, or 2- butene having molecular weight of from 300 to 15,000. b. Unsaturated hydrocarbons, for example polybutadiene, polyisoprene, and copolymers of butadiene and isoprene with olefins such as propylene, butylene and/or aromatic vinyl compounds such as styrene, or vinyl toluene having molecular weights of from 300-15,000.

3. Natural products such as:

Pine tar Colophony Cumarones Linseed oil 4. Synthetic plasticizers such as:

Adipic acid esters Azelaic acid esters Phosphoric acid esters Phthalic acid esters Sebacic acid esters Hydrocarbons of fairly high molecular weight Ethers Thioether esters For more detailed information see l-1.A. Munderloh, Kautschuk und Gummi, Vol. 12 (1959) No. 9, p. WT 246-256 and copending US application Ser. No. 813,688, filed Apr. 4, 1969, and now abandoned.

The recovery step (d) uses the common methods for removing solvents from rubber solutions, e. g. the method of introducing the rubber solution into hot water or a steam destillation process. The oil extended crumbs retained in the recovery step may be dried in any conventional way, e. g. in a drying chamber on a belt drier or in a screw extruder.

The oil-extended rubber obtained by the process described above is distinguished by its outstanding properties. Both its vulcanization behavior characterized by favorable scorch-behavior and crosslinking yield, and also the properties of the vulcanisates such as their tensile strength, modulus, hardness (Shore A) resilience and tear resistance are distinctly superior to those of standard commercial oil-extended polyisoprene. There is a particular marked improvement in the reversion stability of the vulcanisates which can be observed in all ageing processes, for example in the high-temperature vulcanization of heavy-gauge rubber articles and in permanent dynamic stressing such as occurs for example in tires for heavy vehicles.

EXAMPLE 1 Preparation of the catalyst 68 m1 of n-hexane are introduced under nitrogen into a dry vessel equipped with stirring mechanism. A solution of 1.252 g (66 mMols) of titanium tetrachloride in 134 ml of n-hexane and a solution of 0.678 g (59.4

5 mMols) of aluminum triethyl and 0.308 g (23.8

mMols) of di-n-butyl ether in 134 ml of n-hexane, are simultaneously added dropwise while stirring at a temperature of 0C. The brown catalyst suspension formed is stirred for 30 minutes at 0C.

b. polymerization 60 liters of dry hexane and 4,400 g of isoprene are introduced under nitrogen into a dry autoclave equipped with stirring mechanism. The contents of the autoclave are cooled to 8C. under nitrogen. The catalyst suspension is added at that temperature. Polymerization beings immediately without any evidence of a latent period. The heat of polymerization is dissipated by external cooling in such a way that the polymerization temperature rises slowly to 12C. over a period of 3 hours. By this time, a conversion rate of 97percent has been reached. The polymer has a Mooney Viscosity ML4'/100C of 108.

0. Preparation of the oil-rubber and working-up The polyisoprene solution prepared as described in (b) is divided in the absence of air and moisture.

Oil rubber A One half of the polymer solution is admixed with a solution of 2.2 g of bis-( 2-aminoethyl)-amine in 100 ml of benzene, and the resulting mixture is stirred for 15 minutes. A solution of 11 g of N-methyl stearylamine and 1 1 g of 2,6-di-tert.-butyl- 4methylphenol in 250 ml of hexane is then added with stirring. 600 g of a naphthenic extender oil [lngraplast NS are then added and thoroughly distributed by stirring.

The oil-rubber solution thus prepared is freed from the solvent by introduction into water at 92C. The water-moist oil-rubber crumbs are dried for 48 hours at 50 C. in vacuo. Oil content: 28 pphr, ML-4l 100C. 48 Defo (C.) =650/23.

Oil-rubber B, comparison test The other half of the cis-l,4-polyisoprene solution prepared in accordance with (b) is stopped and stabilized with a solution of 1 1 g of 2,6-di-tert.-butyl-4- methyl phenol and 20 g of ethanol in 350 ml of hexane. 600 g of lngraplast NS are then added, and the mixture is stirred until it is completely homogeneous. Oilrubber B is further processed in the same way as oilrubber A. Oil content: 28 pphr Ml-4/100 C. 46 Defo(80 C.) 325/14 The oil-rubber blends prepared in accordance with example 1 were compared with one another, with a natural rubber-oil blend and with two commercial products (lithium type and titanium type), in a series of m corresponding quantities of oil-rubber ""and no oil.

Mixing order on the rollers (400 X 200 m/m) 40 C.

least carbon atoms is added to said catalyst at the same time said aliphatic or cycloaliphatic dior polyamine is added.

3. The process of claim 1 wherein said secondary 5 al1phat1c or cycloaliphatic monoamine containing at Rubber appmx 3 minutes rotation least 10 carbon atoms is added to said catalyst after the 2110 4 minutes add1t1on of said al1phat1c or cycloaliphauc dior ASM 5 minutes polyamme Carbon black stearic acid 7 minutes 4. The process of claim 1 wherein a lower aliphatic g mlmues 10 alcohol 1s added in step (b).

L! p I." minutes Tomlmixingtime 2243 minutes The process of claim 1 wherem the di or poly 3 x narrow, 3 x overturn amine is added to sald catalyst as a solution 1n a TABLE 1 Vulcanlsate data Crude rubber Mixture Elonga- M./kp./

Vulc. Tensil tion at cmfl/H. Shore A E Struct., ML-4 Defo H/E ML-4 Del'o H/E 3 atms., strength, break, kp./4 Product 100 80 100 mius. kpJcin. percent 300% 500% 23 75 23 27 mm 10 145 555 55 131 51 4s 35 44 20 105 520 104 90 51 59 41 51 40 According to Example 1/A 43 500/23 37 500/9 192 490 110 10s 52 51 41 50 38 50 173 490 102 135 52 50 30 49 00 175 500 98 17s 50 5s 30 47 32 10 47 575 33 32 4 20 173 490 39 29 According to Example 1/B 46 325/4 39 500/10 30 175 455 39 45 28 155 450 39 44 20 150 440 33 43 14 10 53 420 32 3s 5 NK/RSS No. 1 plus 25 20 153 490 37 41 25 .h.r. oil 31 400/14 30 157 450 37 44 25 50 133 430 35 41 21 90 113 405 35 3s 13 10 53 500 33 35 5 Commerlcal product 25 20 153 505 39 47 27 p.p.h.r. oil, titanium type 42 500/15 51 775/15 30 150 495 39 50 25 50 405 35 45 17 90 430 37 45 14 10 73 700 34 30 10 Commerleal product 25 20 148 620 40 51 28 p.p.h.r. oil, Li-type 47 1,175/30 55 300/13 30 530 39 33 25 50 125 500 33 49 21 90 115 475 38 47 17 We claim:

1. A process for producing a cis-l,4-polyisoprenerubber extending oil blend which comprises the steps of (a) polymerizing isoprene in solution in an inert aliphatic, cycloaliphatic or aromatic hydrocarbon solvent in the presence of an organo-metallic mixed catalyst consisting essentially of titanium tetrachloride and aluminum trialkyl or aluminum trialkyl etherate or a mixture of aluminum trialkyl and aluminum trialkyl etherate, (b) inactivating said catalyst at the end of polymerization by adding thereto 0.05 to 0.5 percent by weight, based on polyisoprene, of an aliphatic or cycloaliphatic dior polyamine and 0.1 to 1 percent by weight, based on polyisoprene, of a secondary aliphatic or cycloaliphatic monoamine containing at least 10 carbon atoms, (0) incorporating from 15 to 50 parts by weight, based on 100 parts by weight of polyisoprene, of a rubber-extending oil and (d) recovering polyisoprene-rubber extending oil blend from the resulting solution by removing said solvent.

2. The process of claim 1 wherein said secondary aliphatic or cycloaliphatic monoamine containing at hydrocarbon solvent, the resulting solution is washed with water and the secondary aliphatic or cycloaliphatic monoamine containing at least 10 carbon atoms is subsequently added as a solution in a hydrocarbon solvent.

6. The process of claim 1 wherein the aliphatic or cycloaliphatic dior polyamine is 1,2-diamino ethane; l ,2-di( methylamino)-ethane; bis-( 2-aminoethyl amine; 1,1 l-diamino-3,6,9-triazodecane; 1,3-diamino propane; bis-(2-aminopropyl)-amine; 1,4-diamino butane; 1,6-diamino hexane or l,4-diamino cyclohexane.

7. The process of claim 1 wherein said secondary aliphatic or cycloaliphatic monoamine containing at least 10 carbon atoms is di-Z-ethylhexylamine, dicyclohexylamine, N-methyl stearylamine, N-methyl alkylamine wherein said alkyl moiety contains at least 10 carbon atoms or a mixture thereof.

8. The process of claim 1 wherein the secondary aliphatic or cycloaliphatic monoamine containing at least 10 carbon atoms is N-methyl stearylamine. 

2. The process of claim 1 wherein said secondary aliphatic or cycloaliphatic monoamine containing at least 10 carbon atoms is added to said catalyst at the same time said aliphatic or cycloaliphatic di- or polyamine is added.
 3. The process of claim 1 wherein said secondary aliphatic or cycloaliphatic monoamine containing at least 10 carbon atoms is added to said catalyst after the addition of said aliphatic or cycloaliphatic di- or polyamine.
 4. The process of claim 1 wherein a lower aliphatic alcohol is added in step (b).
 5. The process of claim 1 wherein the di- or poly-amine is added to said catalyst as a solution in a hydrocarbon solvent, the resulting solution is washed with water and the secondary aliphatic or cycloaliphatic monoamine containing at least 10 carbon atoms is subsequently added as a solution in a hydrocarbon solvent.
 6. The process of claim 1 wherein the aliphatic or cycloaliphatic di- or polyamine is 1,2-diamino ethane; 1,2-di(methylamino)-ethane; bis-(2-aminoethyl)-amine; 1,11-diamino-3, 6,9-triazodecane; 1,3-diamino propane; bis-(2-aminopropyl)-amine; 1,4-diamino butane; 1,6-diamino hexane or 1,4-diamino cyclohexane.
 7. The process of claim 1 wherein said secondary aliphatic or cycloaliphatic monoamine containing at least 10 carbon atoms is di-2-ethylhexylamine, dicyclohexylamine, N-methyl stearylamine, N-methyl alkylamine wherein said alkyl moiety contains at least 10 carbon atoms or a mixture thereof.
 8. The process of claim 1 wherein the secondary aliphatic or cycloaliphatic monoamine containing at least 10 carbon atoms is N-methyl stearylamine. 